From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <kafai@fb.com>, Hao Luo <haoluo@google.com>
Subject: [PATCH bpf v2] Fix crash due to OOB access when reg->type > __BPF_REG_TYPE_MAX
Date: Thu, 17 Feb 2022 01:49:43 +0530 [thread overview]
Message-ID: <20220216201943.624869-1-memxor@gmail.com> (raw)
When commit e6ac2450d6de ("bpf: Support bpf program calling kernel
function") added kfunc support, it defined reg2btf_ids as a cheap way to
translate the verifier reg type to the appropriate btf_vmlinux BTF ID,
however commit c25b2ae13603 ("bpf: Replace PTR_TO_XXX_OR_NULL with
PTR_TO_XXX | PTR_MAYBE_NULL") moved the __BPF_REG_TYPE_MAX from the last
member of bpf_reg_type enum to after the base register types, and
defined other variants using type flag composition. However, now, the
direct usage of reg->type to index into reg2btf_ids may no longer fall
into __BPF_REG_TYPE_MAX range, and hence lead to out of bounds access
and kernel crash on dereference of bad pointer.
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Hao Luo <haoluo@google.com>
Fixes: c25b2ae13603 ("bpf: Replace PTR_TO_XXX_OR_NULL with PTR_TO_XXX | PTR_MAYBE_NULL")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
--
v1 -> v2
- Use base_type(reg->type) && !type_flag(reg->type) (Alexei)
---
kernel/bpf/btf.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index e16dafeb2450..3e23b3fa79ff 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5688,7 +5688,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
}
if (check_ptr_off_reg(env, reg, regno))
return -EINVAL;
- } else if (is_kfunc && (reg->type == PTR_TO_BTF_ID || reg2btf_ids[reg->type])) {
+ } else if (is_kfunc && (reg->type == PTR_TO_BTF_ID ||
+ (reg2btf_ids[base_type(reg->type)] && !type_flag(reg->type)))) {
const struct btf_type *reg_ref_t;
const struct btf *reg_btf;
const char *reg_ref_tname;
@@ -5706,7 +5707,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
reg_ref_id = reg->btf_id;
} else {
reg_btf = btf_vmlinux;
- reg_ref_id = *reg2btf_ids[reg->type];
+ reg_ref_id = *reg2btf_ids[base_type(reg->type)];
}
reg_ref_t = btf_type_skip_modifiers(reg_btf, reg_ref_id,
--
2.35.1
next reply other threads:[~2022-02-16 20:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-16 20:19 Kumar Kartikeya Dwivedi [this message]
2022-02-16 20:52 ` [PATCH bpf v2] Fix crash due to OOB access when reg->type > __BPF_REG_TYPE_MAX Alexei Starovoitov
2022-02-16 21:00 ` patchwork-bot+netdevbpf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220216201943.624869-1-memxor@gmail.com \
--to=memxor@gmail.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=haoluo@google.com \
--cc=kafai@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).